© 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in.

© 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied,duplicated, or posted to a publicly accessible website, in whole or in part.© 2013 Delmar Cengage Learning. All Rights Reserved. May not be scanned, copied,duplicated, or posted to a publicly accessible website, in whole or in part.

Creating the Image

Unit III

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Radiographic Film

Chapter 19

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Objectives• Describe components of radiographic

film

• Explain production of silver halide crystals

• State purpose of various additives to radiographic film

• Describe latent image formation

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Objectives• Discuss differences between direct

exposure film, screen film, and films for various special applications, such as duplication

• Explain the fundamentals of proper film storage and handling

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Objectives• Identify common radiographic film

artifacts

• Discuss automated and daylight loading film systems

• Explain responsibilities involved in proper radiograph identification

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Photosensitive Film• First image receptor chosen by Röntgen

• No longer most common image receptor because of predominance of digital imaging in 21st century

• Knowledge of film/screen technology still required of radiographers

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Radiographic Film Construction• Base• Adhesive layer

• Emulsion• Supercoat (overcoat)

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Radiographic Film Base• Foundation of radiographic film

– Flexible, yet durable– Uniformly radiolucent– Film must retain its size and shape

throughout use and processing– Thickness ranges from 150-200

micrometers– Modern base is thin sheet of polyester

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Base History• Original base:

– Glass• Plates coated with emulsion

– Difficult maintenance

• Exposure factors with plates very high

• Origin of term “flat plate” of abdomen

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Cellulose Nitrate• Replaced glass plates during World War

I glass shortage

• Highly flammable

• Led to several devastating hospital fires in 1920s and 1930s

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Cellulose Triacetate• Safety base introduced in 1920s

– Less flammable than Cellulose Nitrate

• Disadvantages:– Films would warp with age– Not as resilient as today’s polyester films

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Polyester• Base of today’s modern film

• Introduced in 1960s

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Specializations of Film Base• Blue tint

– Reduces eyestrain– Increases diagnostic accuracy

• Crossover– Light from one screen exposed opposite

emulsion

• Halation

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Cassette Loading• Single emulsion film

– Emulsion side toward intensifying screen

• Emulsion side dull

• Non-emulsion side shiny– LL – notch in film in lower-left corner

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Adhesive Layer• Binds emulsion to film base

– Allows for proper emulsion distribution over base throughout use and processing

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Emulsion• “Heart” of film

• Composed of silver halide crystals suspended in gelatin– Active ingredient photosensitive

• Silver halide crystals

• Typically 5-10 micrometers in thickness

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Gelatin• Allows even distribution

– Separate suspension of silver halide crystals

• Radiolucent

• Non-reactive

• Processing chemistry able to penetrate

• Low Z#

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Types of Silver Halide Crystals• Silver bromide

• Silver iodide

• Silver chloride

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Duplitized Film• Double emulsion or double coated film

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Supercoat/Overcoat• Protective layer of gelatin

– Provides sturdiness to unexposed radiographic film

– Antistatic– Reduces damage from scratches,

pressure, or contamination during storage, handling, and processing

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Manufacturing Radiographic Film• All must take place in total darkness:

– Crystal production– Ripening– Mixing– Coating

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Silver Halide Crystal Formation• First step:

– Pure metallic silver dissolved into nitric acid• Forms silver nitrate

• Second step:– Silver nitrate combined with potassium

bromide

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Silver Halide Crystal Formation• Combination yields silver bromide and

potassium nitrate

• Potassium nitrate is water soluble– Dissolves in water and washes away

during production of emulsion

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Silver Halide Crystal Structure• Resultant shape

can be many varying forms– However, inner

structure takes on cubic form or cubic lattice

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Sensitivity Speck• Silver-gold-sulfide creates imperfections

in crystals– Gives crystals good imaging properties– Result:

• Sensitivity center or sensitivity speck within crystal lattice

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Sensitivity Speck• Allows for collection of many silver

atoms in one area after being exposed to x-ray or light photons

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Ripening• Length of time crystals need to grow

– Size and emulsion influence film factors

• After ripening complete:– Emulsion cooled– Shredded and washed

• Removes potassium nitrate

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Mixing• Shredded emulsion heated and melted

– Specific temperature– Sensitizes crystals

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Mixing• Several extra ingredients may be added

– Dyes• Adjust spectral sensitivity

– Fungicide/bactericide– Antifogging agents

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Spectral Sensitivity• Panchromatic

– Sensitive to all wavelengths

• Orthochromatic– Not sensitive to red

• Controlled by dyes added during mixing

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Coating• Requires precise and expensive

equipment

• Generates 40” rolls of film

• Layers on adhesive, then emulsion, then supercoat

• Film cut to size

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Latent Image Formation• Gurney-Mott Theory (1938)

• X-ray and light photons deposit energy into silver halide crystals

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Latent Image Formation• Energy disrupts bonds between atoms

of crystal– Electron freed– Halide migrates into gelatin– Silver ion remains

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Latent Image Formation• Sensitivity speck “traps” electron

• Silver ion attracted to sensitivity speck to neutralize it

• Process repeats itself

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Types of Film• Direct exposure (nonscreen)

• Intensifying screen

• Duplication

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Film Storage and Handling• Prior to exposure:

– Storage• On end

– Age• Expiration dates

– Rotate stock

– Heat• Below 68ºF (20ºC)

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Film Storage and Handling• Prior to exposure:

– Humidity• 30-60%

– Light– Radiation

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Film Identification• Each exposure must include medical

record information– Date of exposure– Full name of patient– Name of institution– Name of ordering physician– Patient identification number– Type of exam